The Pinkie Ring - S2.E36

Company man Ishii Hirowaka is a heavy drinker, but must quit to avoid liver damage. However, he succumbs to pressure from his workmates and goes out drinking again, ignoring the paper pinkie ring on his finger from his wife to remind him not to drink. Moguro offers to help him quit and gives him a gold ring that painfully squeezes his finger if he drinks alcohol. initially it is effective, however Ishii is invited to drink with his boss and a client, so he removes the ring. When Ishii puts it back on, Moguro makes the ring shrink so tightly that it severs Ishii's finger.